JPH09160336A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation of the quality of an image, which is caused by scattering of toner in the outline part of a transfer image, by making color density low in a range within which the color density of specified outline font and the outline part of the image are converted. SOLUTION: A controller 1 is equipped with a main control part 11, ROM 12, RAM 13, and font storage part 14. The main control part 11 is equipped with an image data control means 111 and so on, controls the entire color image forming device in accordance with a program stored in the ROM 12, and develops a print image onto the RAM 13. The image data control means 111 develops the print image onto the RAM 13 in accordance with the program stored in the ROM 12. An outline part specifying means 112 specifies the range within which the color density of the outline part of the image data developed by the image data control means 111 is converted. A color density conversion means 113 makes the color density in the range specified by the outline part specifying means 112 low according to the combinations of colors, C, M, Y, and K, so as to prevent toner scattering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus, and more particularly to prevention of deterioration in quality of transferred images.

[0002]

2. Description of the Related Art A color image forming apparatus stores and prints image data sent from, for example, a scanner and a host apparatus, and is used in a copying apparatus, a facsimile apparatus or a printer apparatus. The color image forming apparatus is a control apparatus for full-color image data input from a scanner device or the like, and C (cyan), M (magenta), Y
The data of each color (yellow) and K (black) is separated, and the data of the black color component is first sent to the writing optical unit. The writing optical unit forms an electrostatic latent image of a black color component on the photoconductor drum based on the image data of the black color component. At this time,
Only the black toner is emitted from the developing device to form a black toner image on the transfer drum. The transfer drum transfers the black toner image onto the intermediate transfer belt. The color image forming apparatus repeats this operation in the order of the image data of the cyan color component, the image data of the magenta color component, and the image data of the yellow component, so that K, C, M, and Y on the intermediate transfer belt can be performed.
The toner images for the colors are superimposed. After that, the color image forming apparatus feeds the transfer paper from the paper feed unit, and at the transfer unit, the toner images of four colors K, C, M, and Y on the intermediate transfer belt are transferred to the transfer paper at one time. . The conveyor belt sends the transfer paper on which the toner image is transferred to the fixing unit, and the fixing unit fixes the toner image. In this way, the color image forming apparatus prints a color image.

Further, in a color image forming apparatus, when two or more high-density toner images are used in an overlapping manner, for example, in order to print a dark blue image on a transfer paper, both cyan and magenta toners with high density are used. In the case of overlapping, as described above, the image with the magenta toner is transferred after the image with the cyan toner is transferred to the intermediate transfer belt.

[0004]

However, for example, when the cyan toner and the magenta toner are successively superposed at a high density, the intermediate transfer is performed when the image of the magenta toner is transferred as shown in FIG. 14 (c). In some cases, the cyan toner E on the belt hinders the transfer, the magenta toner D is scattered on the intermediate transfer belt, and the color near the edge of the image is not good.

The present invention has been made in order to solve the above disadvantages, and it is an object of the present invention to prevent deterioration of image quality due to toner scattering in the contour portion of an image to be transferred.

[0006]

A color image forming apparatus according to the present invention has a contour part specifying means and a color density converting means, and the contour part specifying means transfers an outline font to be transferred and a color density of a contour part of an image. When the toner density is overlaid on the intermediate transfer belt by reducing the color density of the outline font specified by the outline specifying means and the range of converting the color density of the outline of the image The toner scattering is prevented, and the deterioration of the image quality due to the toner scattering at the transferred characters and the outline portion of the image is prevented.

Further, the color density converting means changes the color density in the range specified by the contour specifying means to prevent the color of the contour from becoming light.

Further, it is preferable that the outline specifying means changes the range of converting the outline font to be transferred and the color density of the outline of the image to prevent toner scattering.

Further, the outline specifying means changes the range of converting the outline font to be transferred and the color density of the outline of the image, and the color density converting means changes the color density of the range specified by the outline specifying means. The color of the image may be reproduced accurately.

Further, according to the outline font to be transferred and the size of the image, the outline part specifying means changes the range for converting the color density of the outline font to be transferred and the outline part of the image, and the color density converting means makes the outline part. It is preferable to change the color density within the range specified by the specifying means.

Further, according to the thickness of the outline font to be transferred, the outline specifying means changes the range of converting the color density of the outline of the outline font to be transferred, and the color density converting means specifies the outline specifying means. It is desirable to change the color density within the above range.

Further, according to the type of the font of the outline font to be transferred, the outline specifying means changes the range for converting the color density of the outline font to be transferred and the outline of the image, and the color density converting means specifies the outline. The color density in the range specified by the means may be changed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A color image forming apparatus of the present invention includes, for example, a control device, a writing optical unit, a photosensitive drum,
It has a developing device, an intermediate transfer belt, a transfer section, a conveyor belt, a fixing section and a sheet feeding section, and sequentially superimposes single color images of different colors on the intermediate transfer belt and transfers the color image superimposed on the intermediate transfer belt to the transfer paper. And is used for a copying machine, a facsimile machine or a printer.

In a color image forming apparatus, for example, when both cyan and magenta toners are sequentially superposed in high density to produce a dark blue color, the cyan toner on the intermediate transfer belt hinders the transfer and magenta. In some cases, the toner was scattered on the intermediate transfer belt and the colors near the edges of characters and images were not good. When printing a color image, there are 9 combinations of C, M, Y, and K colors depending on the color of the image to be printed (4 combinations of 2 colors, 4 combinations of 3 colors, 4 combinations of 4 colors). There are a total of 9 combinations with 1 combination.) If the density of each color in each combination is below a certain value, the toner scattering does not occur.Therefore, the amount of toner for the outline font and the outline portion of the image to be transferred based on the combination by the color density conversion means of the control device is set. It is something to reduce. Here, if the toner density of the entire image is changed, the color of the entire image becomes lighter. Therefore, the outline font to be transferred by the outline specifying means of the control device and the range of changing the color density of the outline of the image are specified. The converting means changes only the density of the contour portion specified by the contour specifying means to reduce the influence on the image. In addition, since the overall impression may change depending on the size of characters and the like, the change in the image is prevented as follows.

Further, when the outline font to be transferred and the image are large or thick, even if the toner density of the entire contour portion is reduced, the influence on the entire image is small.
If the outline font to be transferred and the image are small or thin, reduce the toner density of the entire outline,
Since the color density of the entire image becomes lighter, the color density conversion unit prevents the color of the entire image from becoming lighter by reducing the density of the toner in the contour portion in a dotted line or chain line at regular intervals.

For the same reason, the outline part specifying means reduces the toner density when the outline font and image to be transferred are large and thick, and the outline part to be transferred is thick, and the outline font and image to be transferred are small. If the case is thin or narrow, the width of the range for converting the outline font and the color density of the outline portion of the image is narrowed.

If the range for converting the color density of the outline portion of the outline font or the toner density is changed according to the type of the typeface of the character to be transferred, it is necessary to judge the size of the outline font. Without it, the judgment becomes easier.

[0018]

FIG. 1 is a block diagram of a color image forming apparatus according to an embodiment of the present invention. As shown in the figure, the color image forming apparatus includes a control device 1, a writing optical unit 2, a photosensitive drum 3, a developing device 4, an intermediate transfer belt 5, a transfer unit 6, a conveyance belt 7, a fixing unit 8 and a paper feeding unit 9. Have. The control device 1
As shown in FIG. 2, the main controller 11, the ROM 12, and the RAM 1
3 and a font storage unit 14. The main control unit 11 includes an image data generation unit 111, a contour portion identification unit 112, a color density conversion unit 113, and a print control unit 114, and RO
The entire color image forming apparatus is controlled according to the program stored in M12, and the image to be printed is developed on the RAM 13. The image data generation unit 111 stores the image to be printed in accordance with the program stored in the ROM 12 as RA.
Image development on M13. The contour specifying unit 112 specifies a range in which the color density of the contour of the image data developed by the image data generating unit 111 is converted. The color density conversion unit 113 thins the density of the color in the range specified by the contour specifying unit 112 according to the combination of C, M, Y, and K colors so that toner is not scattered. The print control means 114, for example, C, M, Y, K
In this order, it is sent to the writing optical unit 2 via the page memory 131 in the RAM 13 to perform the printing process.

Upon receiving the cyan monochromatic image data from the print control means 114, the writing optical section 2 converts the cyan monochromatic color image data received from the print control means 114 into an optical signal, and outputs the light corresponding to the original image. A writing process is performed to form a C toner image on the photosensitive drum 3 as an electrostatic latent image. The C toner image formed on the photosensitive drum 3 is transferred to the photosensitive drum 3
When a predetermined bias voltage is applied to a transfer bias roller (not shown) while the intermediate transfer belt 5 and the intermediate transfer belt 5 are in contact with each other, the transfer is performed on the intermediate transfer belt 5. After the C toner image is transferred to the intermediate transfer belt 5, the print control unit 114
Similarly sends monochromatic image data in the order of M, Y, K to the write control unit 2, and the write control unit 2 sequentially superimposes the image data on the intermediate transfer belt 5. The intermediate transfer belt 5 transfers the formed toner image onto a transfer paper. The conveyor belt 7 conveys the transfer paper on which the toner image has been transferred to the fixing unit 8 and transfers the transfer paper to the fixing unit 8.
Fixes the toner image on the transfer paper. In this way, the color image forming apparatus prints a color image.

The main control unit 11 of the color image forming apparatus having the above-mentioned configuration develops the image of the character "a" and develops it in the page memory 13.
The operation of writing to 1 will be described with reference to the flowchart of FIG.

When the main control section 11 receives a printing character "a" from, for example, a scanner (not shown), the image data generating means 111 rasterizes the printing character "a" (step S1). After rasterizing the characters to be printed, the image data generation unit 111 checks whether or not the characters to be printed use two or more colors. If the characters to be printed are black and white characters (step S2), the rasterized characters are selected. The density is adjusted and the image is drawn in the page memory 131 (step S
3).

When the character to be printed uses two or more colors, for example, a dark blue character, the outline is based on the character rasterized by the image data generating means 111 as shown in FIG. 4A. The copy identifying means 112 draws an outline font as shown in FIG. 4B in the work area of the RAM 13 (step S4). Note that, in FIG. 4, the tip portion A of the character “a” shown in FIG.
Only shows. Hereinafter, in the drawings used for the description, only the tip portion A of the character "a" is shown.

Since the dark blue graphic is made by superimposing the cyan graphic and the magenta graphic, the color density converting means 113 converts the rasterized dark blue character shown in FIG. 6A into the dark blue graphic shown in FIG. 6B. The image data is decomposed into cyan single color image data as shown and magenta single color image data as shown in FIG. In the figure, a and b indicate the color densities of cyan and magenta, respectively.
It is "0" and "150". After that, the color density conversion means 113
Is based on the image data of only the contour portion previously created as shown in FIG. 7A, the image data and the magenta of the cyan monochromatic contour portion as shown in FIGS. 7B and 7C. Image data of a monochromatic contour portion is created. Color density conversion means 11
In order to prevent toner scattering, FIG. 3 shows the densities of the image data of the cyan monochromatic contour portion and the image data of the magenta monochromatic contour portion shown in FIGS. 7B and 7C as shown in FIG. 7D.
And conversion as shown in FIG. 7E (step S
5). In the figure, c and d respectively represent cyan and magenta color densities, and their values are, for example, "160" and "100".

After that, the color density converting means 113 operates as shown in FIG.
The cyan monochromatic image data shown in (b) and the magenta monochromatic image data shown in FIG. 6 (c) are drawn in the page memory 131 (step S6), and subsequently the cyan monochromatic outline font shown in FIG. 7 (d). Then, the magenta single color outline font shown in FIG. 7E is overwritten (step S7). In this way, the color density conversion processing unit 113 decomposes the rasterized image data of the character "a" into the cyan single-color image data and the magenta single-color image data shown in FIGS. 8B and 8C. FIG.
As shown in (b) and FIG. 8 (c), the cyan single-color image data and the magenta single-color image data have the density of the outline portion so thin that toner does not scatter. When the image data of is superimposed on the intermediate transfer belt 5 via the photoconductor drum 3,
The image has a step in the density of the contour portion as shown in FIG. In this way, by making the density of the contour portion lighter, it is possible to prevent the toner from scattering, and prevent the color near the contour portion of the character and the image from being unsatisfactory.

Further, if the density of the combination of C, M, Y and K of the colors to be printed is less than a certain value, the toner will not scatter. Therefore, the contour specifying means according to the combination of C, M, Y and K. Reference numeral 112 denotes a range for converting the outline font to be transferred and the color density of the outline portion of the image, and the color density converting means 113 is a range for converting the outline font specified by the outline specifying means 112 and the color density of the outline portion of the image. The color density of may be variable.

Further, when the transferred figure is large or the line is thick, even if the toner density of the entire contour portion is reduced, the effect on the entire image is small, but when the transferred figure is small or the line is thin, the contour is small. When the toner density of the entire area is reduced, the color density of the entire image is reduced. Therefore, when the character to be printed is a character using two or more colors, the color density conversion processing unit 113 examines the size of the character to be printed and the thickness of the line, and when the line is thin, the FIG. 10 (b) and FIG. 10 (c) as shown in FIG.
When converting the density of the monochromatic image data shown in (3), the density may be reduced with an interval. in this case,
On the intermediate transfer belt 5, a cyan monochromatic toner image and a magenta monochromatic toner image are superimposed, as shown in the sectional view of FIG. 11 and the side sectional view of FIG. As described above, by thinning the toner density of the contour portion at intervals, it is possible to prevent the color of the entire image from being lightened. Note that the information on the thickness of the lines that form characters, etc. is, for example, Light, Mideum, Demi,
Since it is contained in font data like Bold, it is good to use this information for judgment. Further, the interval for reducing the toner concentration may be an interval formed in a dotted line shape or an interval formed in a chain line shape, and these intervals may be freely selected.

For the same reason, when the outline font and image to be transferred are large or thick, the outline specifying unit 112 widens the range of thinning the toner density of the outline so that the outline font and image to be transferred are large. If it is small or thin, the range for thinning the toner density of the contour portion may be narrowed. For example, when the character to be printed is a character using two or more colors, the contour portion identifying unit 112 checks the size of the character or the like to be printed and the thickness of the line, and when the line is thick, 13), the range in which the toner density in the contour portion is thinned is widened, and FIG.
The density is converted as shown in (d) and FIG. 13 (e).
This makes it possible to further reduce toner scattering. Further, when the line is thin, the width of the range where the toner density of the contour portion is thinned is narrowed, so that the color of the entire image can be prevented from being thinned.

When the characters to be printed use two or more colors, the type of the typeface of the character to be transferred is checked, and the toner density is changed as described above according to the type of the typeface of the character to be transferred. Alternatively, the width of the range in which the toner density in the contour portion is reduced may be changed. In this way, by making a determination based on the type of the typeface of characters, it is possible to prevent the color of the entire image from becoming light, and it becomes easy to make a determination when changing the width of the range in which the toner density of the contour portion is lightened.
For example, in the case of the Gothic type, the width of the contour is thick because the thickness of the line is constant, and in the case of Mincho type, the thickness of the line is changed and the width of the contour is thin.

[0029]

As described above, according to the present invention, the toner density is reduced with respect to the range in which the color density of the outline font and the contour portion of the image is converted, and the toner scattering is caused when the toner image is superposed on the intermediate transfer belt. Since it is reduced, it is possible to prevent the quality of the image from being deteriorated due to the scattering of the toner in the characters to be transferred and the outline portion of the image.

Further, since the outline font and the color density of the outline portion of the image are changed, it is possible to prevent the color of the outline portion from being lightened by changing the color density according to the combination of colors.

Further, since the range for converting the outline font and the color density of the outline portion of the image is changed, it is possible to prevent the toner from scattering by performing the optimum color density conversion processing according to the color combination.

Further, since the range for converting the outline font and the color density of the outline portion of the image to be transferred is changed and the color density of the range for converting the color density of the outline font and the outline portion of the image is changed, the toner is scattered. It is possible to perform the optimum color density conversion processing based on the combination that occurs and the combination density.

Further, according to the outline font to be transferred and the size of the image, the range of converting the outline font to be transferred and the color density of the outline portion of the image is changed, and the color density of the range is changed. It is possible to prevent a decrease in the color density of.

Further, the range of converting the color density of the outline portion of the transferred outline font is changed according to the thickness of the transferred outline font, and the color density of the range is changed, so that the color density of the entire image is changed. The thinning can be prevented, and the scattering of the font can be further reduced according to the outline font to be transferred and the thickness of the image.

Further, the range of converting the color density of the outline font to be transferred and the outline portion of the image is changed according to the type of the typeface of the outline font to be transferred, and the color density of the range is changed. It is possible to prevent the color density from becoming thin and to make the judgment easily.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram of a control device.

FIG. 3 is a flowchart showing an operation of converting image data into image data.

FIG. 4 is a transition diagram of image data when image data of a contour portion is created.

FIG. 5 is a configuration diagram showing a configuration of characters to be printed.

FIG. 6 is a configuration diagram of image data decomposed into cyan and magenta.

FIG. 7 is a configuration diagram of image data in which a contour portion is decomposed into cyan and magenta.

FIG. 8 is a configuration diagram of image data showing a density of each dot of a character to be printed.

FIG. 9 is a cross-sectional view of the intermediate transfer belt after the image is transferred.

FIG. 10 is a configuration diagram of image data when the density is changed at regular intervals.

FIG. 11 is a cross-sectional view of the intermediate transfer belt when the density is changed at regular intervals.

FIG. 12 is a side sectional view of the intermediate transfer belt when the density is changed at regular intervals.

FIG. 13 is a configuration diagram of image data when the width of the contour portion is increased.

FIG. 14 is an explanatory diagram illustrating a toner scattering state.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control device 11 Main control unit 111 Image data generation means 112 Contour portion specifying means 113 Color density conversion means 114 Printing control means 14 Font storage section 3 Photosensitive drum 5 Intermediate transfer belt 6 Transfer section

Claims (7)

[Claims] 1. A color image forming apparatus in which monochromatic images of different colors are sequentially superposed on an intermediate transfer belt, and the color images superposed on the intermediate transfer belt are transferred to a transfer paper. The outline specifying means specifies the outline font to be transferred and a range for converting the color density of the outline of the image, and the color density converting means reduces the color density of the range specified by the outline specifying means. A color image forming apparatus, which reduces scattering of toner when a toner image is superposed on an intermediate transfer belt. 2. The color image forming apparatus according to claim 1, wherein the color density conversion means varies the color density in the range specified by the contour specifying means. 3. The color image forming apparatus according to claim 1, wherein the outline specifying unit changes a range for converting the outline font to be transferred and the color density of the outline of the image. 4. A contour part specifying means changes a range for converting a color density of an outline font to be transferred and an outline part of an image, and a color density converting means changes a color density of a range specified by the contour specifying part. Item 1. The color image forming apparatus according to Item 1. 5. The outline part specifying means changes the range for converting the color density of the outline font to be transferred and the outline part of the image according to the size of the outline font to be transferred, and the color density converting part. The color image forming apparatus according to claim 4, wherein the color density of the range specified by the specifying unit is variable. 6. The contour part specifying means changes the range for converting the color density of the contour part of the outline font to be transferred according to the thickness of the outline font to be transferred, and the contour part specifying means specifies the color density converting means. The color image forming apparatus according to claim 4, wherein the color density of the range is varied. 7. The contour part specifying means changes the range for converting the color density of the outline part of the outline font to be transferred, and the color density converting means sets the outline part specifying means according to the type of the typeface of the outline font to be transferred. The color image forming apparatus according to claim 4, wherein the color density of the specified range is changed.